Hybrid Plasmonics

Surface plasmon have recently created a large interest due to their ability to focus light to a subwavelength scale. However, the large propagation loss of surface plasmon is a serious limitation. To overcome this limitation, we have proposed & demonstrated a hybrid plasmonic waveguide which consists of a metal plane separated from a high index medium by a low index spacer. Using this scheme the propagation loss could be reduced by more than an order of magnitude. Currently we are working on novel devices for integrated optics using a hybrid plasmonic guiding scheme. A Surface plasmon is usually excited by use of prism or grating. These excitation schemes are too bulky for nano-photonic applications. We have recently demonstrated that the combination of a sub-wavelength slot and a dielectric waveguide can act as a very compact, low-noise and efficient plasmon excitation scheme.

Dispersion Engineering

Dispersion Engineering lies on the intersection of three important branches of physics and engineering: Electromagnetic theory (EM), communication theory, and matter wave interaction. We are interested in mapping the evolution of information and energy in a dispersive medium/attenuating medium in space and time. More specifically, we are trying to tackle the following question: "Can a medium having abnormal group velocity, in presence of noise, be used to reduce or eliminate signal latency in electronic or microwave interconnects?"

Nanoparticles

The electromagnetic heating of metallic nanostructures (MNS) is caused due to the surface currents generated by the electric field in the metal’s skin depth region. These surface currents are strongly dependent on the surface morphology of the structure. Hence, the absorption of the energy from the incident radiation is strongly dependent on the shape of the surface of the MNS. Such electromagnetic heating becomes especially strong in the wavelength regime of the plasmon resonance of the MNS. This peak plasmon resonant wavelength of the MNS is also strongly dependent on the shape of the structure. For the purpose of energy conversion, besides absorption of energy from the electromagnetic radiation, it is equally important to make a pathway for the generated heat to be transferred to the surrounding medium. This transfer of thermal energy is proportional to the surface area of the object in contact with the surrounding medium, which directly relates on the shape of the object. We have developed a structural optimization method for metal nanostructures based on the shape dependency of their electromagnetic heat dissipation and thermodynamic transfer to the surroundings. We have used a parallel genetic algorithm (GA) in conjunction with a coupled electromagnetic (FDTD) and thermodynamic modeling of the metallic nanostructures for the optimization. The optimized nano-structure demonstrates significant improvement in electromagnetic heating in the spectral window of optimization as well as expedited cooling properties. The symmetry of the structures which is inherent in the design procedure makes them independent of the polarization at normal incidence and insensitive to the azimuthal direction of incidence.

Ultrafast

For the next generation of integrated optics a number of novel materials are needed to allow for high modulation speeds and light generation on chip. To understand the properties of such materials better we use an ultrafast optical parametric amplifier in a pump-probe scheme. This allows to measure & understand the ultrafast carrier dynamics and accordingly optimize the materials for a specific device function.